Hi! I don't think that you have to worry at this point, especially if he's breastfeeding regularly (4+ times per day) that will be meeting all of his nutritional requirements. Before age 1 milk is their main source of *everything*, and solids are really for fun and learning about new tastes and textures.
Around age 1 you want to make sure that he's getting a balanced diet that meets all of his nutritional needs. My ds has a milk allergy and he drinks calcium fortified soy milk - there's also soy cheese, yogourt, etc. If soy is a problem, there is oat milk, rice milk, etc. that could all help to meet his calcium needs. Plenty of non dairy foods have calcium in them too, here's a link with a good list:
http://www.keepkidshealthy.com/nutrition/calcium_non_dairy.htmlhth!